In certain nuclear reaction studies, it is desirable to use a thin oxide film as a target material. Such films, when formed from oxide powders by conventional techniques, are too discontinuous in structure to be self-supporting. When a backing is used to support the discontinuous oxide target material, additional contaminating metals and oxides are introduced.
U.S. Pat. No. 3,242,000 teaches a procedure comprising impregnating an acrylic fiber textile with a solution containing at least one compound having a refractory metal cation, drying the textile, and finally carbonizing the impregnated textile in an atmosphere containing at least some oxygen, preferably at a level of 10 to 20 percent. See particularly col. 2, lines 43 to 57. The patent does not disclose the extent to which the compound having a refractory metal cation is converted to the corresponding refractory metal oxide during subsequent treatment thereof.
U.S. Pat. No. 3,403,008 discloses the preparation of metal carbide containing fibers and textiles derived from a preformed organic polymeric material (including viscose rayon). The process includes impregnating a rayon fabric with a salt of a metal, drying the fabric, carbonizing the dried fabric and thereafter heating the carbonized fabric in a non-oxidizing atmosphere at a temperature sufficient to form a carbonized fabric containing metal carbide.
U.S. Pat. No. 3,400,181 discloses the preparation of a shaped carbon article by first forming any desired shape from cellulose crystallite aggregates obtained from rayon or cellophane (see col. 2, lines 22 to 27) which are mixed either with a metal compound or boron oxide, thereafter drying the shaped article and finally carbonizing the same at a temperature above 400.degree. C. (see col. 1, lines 53 to 75, and col. 4, lines 1 and 18 to 39). A major distinction between the process described by U.S. Pat. No. 3,400,181 and that described in this application resides in the exact composition of the product obtained so far as the metal or boron content is concerned.
U.S. Pat. No. 3,803,056 teaches impregnating a regenerated cellulose fabric such as rayon with a heavy metal salt, drying the impregnated fabric and thereafter carbonizing the dried fabric to produce a carbonized fabric to which the heavy metal is chemically bound, but not in the form of a metal carbide.
U.S. Pat. No. 3,749,151 teaches a method of carbonizing fibrous cellulosic materials which have been loaded with heavy metal compounds such as thorium, lanthanum or the like. See particularly col 8., lines 21 to 26. The patent does not specifically disclose that such heavy metal compounds are converted to metal oxides in the course of the carbonization.
Maier, "IEEE Transactions On Nuclear Science", Vol. NS-28, No. 2, (April 1981), pp. 1576 to 1583, discloses the preparation of free-standing (unsupported) nuclear accelerator targets by various methods.